Embodiments in accordance with the present invention relate to a magnetic head for a disk storage unit using a perpendicular magnetic recording method, particularly, to a write magnetic head structure suitable for recording high density magnetic information on a medium surface and a production method thereof.
A semiconductor memory and a magnetic memory are mainly used for a storage (recording) device of an information appliance. The semiconductor memory is used for an internal storage from the standpoint of access time, and the disk storage unit is used for an external storage from the standpoint of large capacity and nonvolatile properties. A storage capacity is an important index for indicating performance of the disk storage unit, and a smaller disk storage unit having a large capacity is demanded in the market along with recent development of information society. One of recording methods suitable for such demand is a perpendicular recording method. Since this method enables high density, it is considered that the method will become the mainstream method in place of the longitudinal recording method.
[Patent Publication 1] JP-A-2005-92929
[Patent Publication 2] JP-A-2005-190518
[Patent Publication 3] JP-A-2001-250204
[Patent Publication 4] JP-A-2004-164783
Patent Publication 1 discloses an integral shield layer 77 formed over an upper part of a main magnetic pole and both sides of the main magnetic pole and an auxiliary magnetic pole 34 which is connected to a yoke and formed on the shield layer 77. A magnetic path is formed by the auxiliary magnetic pole 34, the yoke 31, and the main magnetic pole 30. A flair is formed on the main magnetic pole 30. A thickness of the shield layer 77 is decided depending on a resist layer R2.
Patent Publication 2 discloses a magnetic head for perpendicular recording which has a main magnetic pole whose width is widened with respect to a trailing side and narrowed with respect to a reading side and is provided with a trailing side shield. A flair is formed on the main magnetic pole, and a thickness of the trailing side shield is controlled by a resist frame pattern 23. It is disclosed that it is necessary to keep the thickness of the trailing shield to a throw height or less since a magnetic field is leaked from the flair portion to the trailing shield when the trailing shield is close to a flair point of the main magnetic pole.
Patent Publication 3 discloses a magnetic write head having a conductor coil disposed in such a fashion as to sandwich a main magnetic pole thin film from two thickness directions of the main magnetic pole thin film, wherein whole parts of the main magnetic pole and the conductor coil are enclosed by a soft magnetic thin film also serving as a magnetic shield.
Patent Publication 4 discloses a structure for reducing a magnetic flux density in a backing layer by preventing deterioration in recording magnetic field strength by the use of asymmetric magnetomotive forces for exciting a main magnetic pole through provision of an excitation coils different in magnetomotive force on both side of the main magnetic pole in such a fashion as to sandwich the main magnetic pole.
As a result of study conducted by the inventors, the following problems are detected. Since an orientation of magnetization of a recording medium of the perpendicular recording method is in a perpendicular direction with respect to a surface of the medium, a degree of influence of a demagnetizing field to be exerted between adjacent magnetic domains is lower as compared with that of the longitudinal recording method. Accordingly, it is possible to write high density magnetic information on the medium and to form a large capacity magnetic disk; however, it is necessary to control a length in a depth direction of the soft magnetic film (shield used for achieving a steep magnetic field gradient) disposed close to the main magnetic pole to be short with high accuracy. In order to generate a ferromagnetic field, it is necessary to control the flair point of the main magnetic pole with high accuracy. Further, since a recording magnetic field is reduced by a large scale when the length in the depth direction of the soft magnetic film contacting both sides of the main magnetic pole, it is necessary to accurately control formation precision (film thickness, length in depth direction) of the members in order to achieve the desired steep magnetic field gradient. More specifically, it is required that the length in the depth direction of the soft magnetic film (shield used for achieving steep magnetic field gradient) disposed close to the main magnetic pole and the flair point of the main magnetic pole have the sizes of from 50 to 200 nm, which are very small, and a manufacturing error is about □ 10 nm, which is of remarkably high accuracy. Though the thickness of the auxiliary magnetic pole is controlled with the use of the resist in Patent Publication 1, positioning is difficult in actuality. Therefore, in the case of producing the perpendicular head by a commercially available semiconductor production apparatus, a production yield is low, and it has been difficult to produce cheap heads in a sufficiently large amount.
Also, a technology of disposing a two-layer coil on both sides of the main magnetic pole is effective for generating a strong recording magnetic field. In this case, too, it is necessary to control the length in the depth direction of the soft magnetic film disposed close to the main magnetic pole and the position of the flair point of the main magnetic pole. Since it is also important to perform heat reduction in the constitution of disposing the two-layer coil on both sides of the main magnetic pole, it is necessary to take the shape of the coil into consideration.
An object of this invention is to provide a magnetic head having a narrow track width and excellent in bulk production for the purpose of realizing a disk storage unit having large capacity and capable of high speed recording.